An electronic device such as a mobile device includes a high-frequency circuit that connects a transmission circuit or a reception circuit to an antenna. The high-frequency circuit has a high-frequency switching circuit to selectively connect the transmission circuit or the reception circuit to the antenna. A HEMT (High Electron Mobility Transistor) using GaAs is frequently used for switching elements of the high-frequency switching circuit. However, to enhance the function of the switching circuit and reduce the price thereof, application of a MISFET (Metal Insulator Semiconductor Field Effect Transistor) using Si is examined in recent years.
It is preferable that the switching elements of the high-frequency switching circuit pass high-frequency signals to the antenna without degrading the signals. That is, insertion losses of the high-frequency signals are preferably smaller. To reduce the insertion losses of the high-frequency signals, it is important to lower on-resistances of the switching elements. To lower the on-resistances of the switching elements, not only a channel length (a gate length) needs to be shortened but also a gate dielectric film needs to be thinned.
However, when the gate dielectric film is thinned, an electric field concentrates on a drain extension layer located just under a gate electrode due to a voltage difference between a gate and a drain and GIDL (Gate-Induced Drain Leakage) is likely to occur when the switching element is in an off-state. Because an off-state breakdown voltage of the switching element is thus lowered, the voltage difference between the gate and the drain at the time when the switching element is in an off-state needs to be reduced. This means that input power (allowable input power) of the high-frequency switching circuit needs to be reduced.
As described above, when the MISFET is applied to the switching elements of the high-frequency switching circuit and the film thickness of the gate dielectric film is reduced to reduce the insertion losses of the high-frequency signals, the off-state breakdown voltage is lowered due to the GIDL. This causes a problem that allowable input power of the high-frequency switching circuit cannot be maintained.